h a l f b a k e r yAssume a hemispherical cow.
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First, we start with a heatsink which we can spin,
vaguely similar to this one [link].
Then, we give it a very thin coat of thermally
conductive white paint.
Next, instead of putting the heatsink on top of
something needing cooling (such as an IC), we put our
components which need cooling
(our LEDs) on top of
the heat sink.
The spinning of the heatsink creates air flow, which
keeps it (and the LEDs attached to it) cool.
By operating at a lower temperature, the rate of
decrease of the luminous efficiency of the LEDs is
reduced... or in other words, they last longer.
Perhaps equally important, if the heatsink is spinning
fast enough, each LED will appear to be a circle of
light, instead of a dot of light. This makes the light
appear more diffuse.
If each LED is mounted at a different radius, the
spinning, lit up, heatsink will appear to have several
concentric rings of light on it. This makes the light
even more diffuse.
There will be a certain amount of noise, but if the
motor is quiet, and the heatsink fins are the right size
and shape, and the LEDs don't produce excessive
turbulence, then the noise level will be relatively low.
Sandia's spinning heatsink
https://share.sandi...ws_releases/cooler/
Who'd've thunk that air bearings would have such a high rate of heat transfer? [goldbb, Mar 29 2013]
Sulfur Lamp
http://en.wikipedia.org/wiki/Sulfur_lamp
Uses rotation to assist heat distribution. [spidermother, Mar 31 2013]
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Some of you might be wondering, why LEDs need
cooling, when they supposedly "don't produce heat." |
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The answer is simple: Although LEDs produce much
much less heat than the incandescent lamps they
replace, they are not completely heat-free. |
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For example, GE's upcoming LED-based replacement for
a 100W incandescent lamp uses 27W, and it will make
at least as much heat as a 23W incandescent lamp. |
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Since LEDs are extremely sensitive to heat, not having
enough cooling could drastically reduce the lamp's
operating life... which would be very "not cool" when
the lamp could cost as much as $100. |
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Seems like the weak link would be the commutator- how many hours can those last? |
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You would tap into the motor commutator, I imagine. |
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Just make it an induction motor: no commutator and it runs natively off of AC. Typically the conductors in a squirrel cage rotor are high current low voltage already which is good for powering the LEDs. I suppose the design would be quite different that an induction motor in existance since that would need to be an extremely small motor (probably much less power than a pager vibrator motor), yet the coils would have to transfer extra power to the rotor to power the LEDs. |
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//
Seems like the weak link would be the commutator-
how many hours can those last? // |
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The bearing is a weak link. How often do cooling fans
fail, or hard-disks don't start up? |
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In [scad]'s configuration, the induction motor would also act as ballast for the LEDs. |
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